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Abstract: PO2133

SIRPα Interacts with the IGF-1 Receptor in CKD-Induced Cardiomyopathy

Session Information

Category: Hypertension and CVD

  • 1403 Hypertension and CVD: Mechanisms

Authors

  • Wu, Jiao, Baylor College of Medicine, Houston, Texas, United States
  • Mitch, William E., Baylor College of Medicine, Houston, Texas, United States
  • Thomas, Sandhya S., Baylor College of Medicine, Houston, Texas, United States
Background

A major consequence of chronic kidney disease (CKD) is associated with cardiomyopathy. Even at early stages of CKD with near normal GFR, and normal blood pressure, left ventricular hypertrophy (LVH) is present, which suggests an unidentified trigger unrelated to pressure overload. We now find that elevations of signal regulatory protein alpha (SIRPα), a substrate for tyrosine phosphatases, in cardiac muscle adversely influences insulin signaling via interactions with the insulin-like growth factor-1 receptor (IGF-1R) in CKD.

Methods

SIRPα floxed (control) vs. muscle-specific (mSIRPα) KO mice were subjected to subtotal nephrectomy. The binding affinity between IGF-1R immunoprecipitate lysates and purified recombinant SIRPα was determined based on the association rate (ka) and the dissociation rate (kdis) constants using bio-layer interferometry (BLI; Octet RED384 systems). Finally, SIRPα vs. GFP plasmids were transfected into muscle cells. n=4-6 mice/group, results are presented as mean ± SD.

Results

Control mice with CKD displayed reduced levels of tyrosine phosphorylation of IGF-1R in cardiac muscle. However, in mSIRPα KO mice with CKD there was no downregulation of IGF-1R phosphorylation despite the presence of CKD. Next, we examined the interactions of these proteins by immunoprecipitation analysis. SIRPα proteins were immunoprecipitated and immunoblotted with the IGF-1R confirming interactions. IGF-1R-SIRPα interactions were further validated using the BLI to assess protein quantities and characterization of kinetics. Specifically, IGF-1R was immunoprecipitated from cardiac muscle and the binding kinetics of Fc-tagged-recombinant SIRPα (rSIRPα) to the IGF-1R was identified via BLI. We concluded that rSIRPα was bound to immunoprecipitated IGF-1R with a kD of 147 uM, which futher validate their interactions. Lastly, SIRPα plasmids were transfected into myotubes, which led to an upregulation of SIRPα and impaired activation of insulin signaling mediators (IGF-1R and pAKT) plus worsening muscle fibrosis when compared to control transfected cells.

Conclusion

SIRPα interacts with the IGF-1R reducing receptor activities, confirming its role in regulating insulin/IGF-1 intracellular signaling in cardiac muscle while exacerbating cardiac muscle functions in CKD.

Funding

  • Veterans Affairs Support